Compared with the common mould material, the alloy mould material has more excellent thermal property and more efficient heat transmission. On the aspects of improving the quality, shortening the production cycle, simplifying the mould and cooling the water-race maintenance, the alloy mould plays an important role.
There are three primary indicators to judge the thermal property of the alloy mould material, namely thermal conductivity, thermal diffusivity and the efficiency of the heat transmission. The high thermal conductivity can make the material transfer more heat quantities at the unit time. The high thermal diffusivity can ensure the mould realizes the heat balance very quickly when the temperature is changed and faster adapts the changes of the temperature. As for the heat transmission efficiency, it represents the instant efficiency when the heat is transferred from the high temperature object to the low temperature object. In the forming process, the thermal property of the alloy material has a great effect on the different stages of the heat transmission for the mould. When the heating temperature of the mould achieves the processing temperature, the excellent capacity of the thermal diffusion can promote the alloy mould to establish the heat balance and the forming process will start. When the hot melt material enters the mould and makes the mould cool down, the relatively high efficiency of the heat transmission means that the heat of the mould will begin to come out from the molten material quickly. The high efficiency of the thermal diffusion is of great help for the mould to achieve the heat balance. Once the balance is achieved, the thermal conductivity will decide the time of the demould time. At the stages of the mould opening, demoulding and mould closing, the high thermal diffusivity can help the mould maintain the temperature of the balance point.
The alloy mould with high thermal conductivity is very helpful for the machine shaping of the two main polymers, namely amorphous polymer and semi-crystalline polymers and also can obviously reduce the time for cooling down. What’s more, for all plastic raw materials, the alloy mould with high thermal conductivity can make a great contribution to the shorter production period and better cooling effectiveness. The amorphous polymer is characterized by the loose and random molecular and meanwhile it has no melting point. When the temperature is heated to the vitrification temperature, the viscosity of the polymer will be reduced and begin to flow freely. When the mould can be filled by the melting material, the heating can be stopped. Then, the heat can be transferred again, until the temperature of the polymer is reduced to the vitrification temperature. The semi-crystalline polymer, including nylon, polythene, polypropene, polyformaldehyde and so on, is featured by the tight molecular and the structure of the molecular is the same. In the manufacturing process, these polymers are in the melting state. When the temperature is reduced, they become the semi-crystalline material. For the above-mentioned manufacturing conditions, the alloy mould with high heat conductivity can satisfy them.
Post time: 05-19-2017